Personally, I'd probably get the excellent 85 f/1.8 and have done with it. It's a light weight and very sharp lens as well as being pretty versatile. You've got that kit lens and flash to handle anything you really need. I think the 85 will also do fine to take pictures of her little feet and hands from back away enough to not wake her or intimidate her when you don't want to. It also produces a very flattering perspective for all around portraiture. The lens sells for only $499 as is a real bargain.

If not that, I'd get the excellent $219 Nikkor 50 f/1.8 which serves as a fairly wide portrait lens and can get in pretty tight if need be.

I'd try one of those before looking a macro lenses. Both of the above will get you pretty close as will your kit lens or the 70-300 in a pinch. Try these before you buy or consider a macro lens.

Agree with Craig here, 85mm will work out longer on a D90 mind, around 127mm with the crop factor so indoors can be tight. That's why a 50mm f/1.4 may be more useful as it will act around an 80mm lens on DX. And if you ever upgrade you can use these lenses on FX. The 35mm 1.8 you wouldn't be able to, also it's not as good for portraiture in terms of subject isolation and the quality of the backgrounds (bokeh).